The present invention relates to a substrate assembly apparatus that, when forming a liquid crystal display, drops liquid crystal to a substrate on a table and then bonds substrates together using an adhesive applied to either one of substrates placed on a pressure board side or on the table.
An apparatus disclosed in Japanese Patent Laid-open No. Hei 10-26763 is known as an apparatus for manufacturing a liquid crystal display panel. Disclosed in this publication is a procedure that flows as follows. Specifically, a first of two glass substrates having transparent electrodes and thin film transistor arrays disposed thereon is coated with liquid crystal and spacers are disposed dispersedly. A second of the two glass substrates is then placed on the first glass substrate using a pin having a vertical motion mechanism. The second glass substrate is positioned correctly using positioning pins disposed in a crosswise direction of the apparatus. A chamber is then vacuumized and the two glass substrates are overlapped with each other and positioned correctly again. The pressure inside the chamber is then returned to the atmospheric side pressure to complete the bonding process.
Japanese Patent Laid-open No. 2001-305563 discloses an arrangement having an integrated vacuum chamber that includes therein a first table and a second table. A first of two substrates is removably fixed to an upper surface or a lower surface of the first table. A second of the two substrates is removably fixed to a lower surface or an upper surface of the second table. The first and the second tables are disposed such that the upper and lower surfaces, to which the respective substrates are fixed, oppose each other. One of the two tables is coupled to the vacuum chamber via an elastic body airtightly and movably. The table includes drive means that move at least in a horizontal direction relative to the vacuum chamber toward an atmospheric side of the vacuum chamber partitioned by the elastic body.
Japanese Patent Laid-open No. 2001-5401 discloses a substrate assembly apparatus having two chambers, an upper and a lower chamber. The lower chamber includes a substrate transport unit and a liquid crystal dispensing unit.
Further, Japanese Patent Laid-open No. 2004-233473 discloses an arrangement including a lower frame and an upper frame mounted on a mount. The lower frame includes a first Z-axis drive mechanism that largely moves the upper frame vertically. The lower frame includes a lower chamber disposed thereinside. The upper frame includes an upper chamber disposed thereinside. The upper chamber includes an upper table disposed thereinside. The lower chamber includes a second Z-axis drive mechanism disposed on a lower side thereof. The second Z-axis drive mechanism moves a lower table disposed inside the lower chamber vertically over a micro-distance. The lower chamber further includes a drive mechanism disposed on a side surface thereof. The drive mechanism moves the lower table horizontally. The upper frame and the lower frame are then united together. This causes the upper chamber and the lower chamber to be united together via a seal ring and thus a vacuum chamber to be formed.
In the aforementioned Japanese Patent Laid-open No. Hei 10-26763, the substrates are pressurized only by using a differential pressure between a pressure between the substrates and a pressure on the outside of the substrates. This makes it necessary to make sure that a sealant between the substrates reliably and positively fills the space between the two substrates. This requires a greater amount of sealant and there is also a likelihood that the sealant will spread over to a display side. In addition, while the lower substrate is held in position in a vacuum by being placed on a flat stage, the upper substrate is supported at appropriate positions along a circumference thereof by pin-like members. As a result, a large-sized substrate measuring 2 m×2 m or more flexes, which makes it difficult to position accurately the upper and lower substrates.
Furthermore, the upper and lower substrates are directly transported into the vacuum chamber and the vacuum chamber is then exhausted and vacuumized from the atmospheric pressure. However, this exhaustion takes a long time, posing a problem of the arrangement's inability to enhance productivity.
With the trend in the substrate becoming bigger as represented in the arrangement disclosed-in Japanese Patent Laid-open No. 2001-305563, the vacuum chamber itself becomes bigger. In a conventional system using a gate valve for loading and unloading of substrates, in particular, the vacuum chamber itself is made even bigger. This makes it difficult to load and unload substrates and perform maintenance jobs. To fix a substrate to the upper table (pressure plate) and fix and position another substrate to the lower table, the lower chamber may be moved as disclosed in Japanese Patent Laid-open No. 2001-5401. The lower chamber in this case weighs excessively heavily, thus requiring an inordinate driving force. This poses another problem.
The arrangement of a bonding apparatus as disclosed in Japanese Patent Laid-open No. 2004-233473, on the other hand, requires driving mechanisms, one for moving the upper frame vertically and one for moving the upper table or lower table vertically. This makes the apparatus bigger in size and heavier in weight.
The apparatus disclosed in Japanese Patent Laid-open No. 2004-233473 uses a ball spline in a guide mechanism for moving the upper frame vertically. It is therefore likely that a kind of rigidity required in a large-size apparatus cannot be achieved.
Furthermore, the upper and lower tables for holding substrates in large-sized bonding apparatuses must have a flat surface of high accuracy so that uneven pressure during bonding may not occur. It is nonetheless difficult to achieve such flatness of the surfaces in large-sized bonding apparatuses.